Cells as the Basic Units of Living Organisms (Cambridge (CIE) AS Biology): Flashcards
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What is the function of the cell surface membrane?
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What is the function of the cell surface membrane?
A partially permeable membrane made of phospholipids and proteins.
It controls the movement of substances into and out of the cell.
Outline the structure and function of the nucleus.
Contains the cell's DNA, surrounded by a double-membraned nuclear envelope with nuclear pores.
It controls the cell's activities.
The nucleolus inside makes ribosomes.
What is the function of the rough endoplasmic reticulum (RER)?
A system of flattened membrane sacs studded with ribosomes.
It synthesises and transports proteins.
What is the function of the smooth endoplasmic reticulum (SER)?
Membrane sacs without ribosomes.
It synthesises, stores and transports lipids and steroids.
Outline the function of the Golgi body.
A stack of flattened membrane sacs.
It modifies, packages and sorts proteins and lipids into vesicles for secretion.
It also forms lysosomes.
Outline the structure and function of a mitochondrion.
Surrounded by a double membrane; the inner membrane is folded into cristae.
It is the site of aerobic respiration, producing ATP.
It contains small circular DNA and 70S ribosomes.
What is the function of ribosomes, and where are 80S and 70S ribosomes found?
Ribosomes are the site of protein synthesis.
80S ribosomes are found in the cytoplasm.
70S ribosomes are found in chloroplasts and mitochondria.
What is the function of a lysosome?
A membrane-bound sac containing digestive (hydrolytic) enzymes.
It breaks down worn-out organelles, waste materials and pathogens.
Outline the structure and function of a chloroplast.
Surrounded by a double membrane; contains stacks of membranes called grana and a fluid stroma.
It is the site of photosynthesis.
It contains small circular DNA and 70S ribosomes.
What are the functions of centrioles and microtubules?
Microtubules are hollow tubes of protein that form the cytoskeleton, giving shape and moving organelles.
Centrioles are bundles of microtubules that form the spindle during cell division.
Distinguish between cilia and microvilli.
Cilia are hair-like projections that beat to move substances across the cell surface.
Microvilli are folds of the cell surface membrane that increase surface area for absorption.
What are the functions of the cell wall and plasmodesmata in plant cells?
The cell wall is made of cellulose and provides support, preventing the cell from bursting.
Plasmodesmata are channels through cell walls that connect the cytoplasm of neighbouring cells.
What are the functions of the large permanent vacuole and tonoplast in plant cells?
The vacuole stores cell sap and helps keep the cell turgid (firm).
The tonoplast is the membrane surrounding the vacuole; it controls what enters and leaves.
The structure inside the nucleus that makes ribosomes is the .
The structure inside the nucleus that makes ribosomes is the nucleolus.
Which structures are found in plant cells but not in animal cells?
Cellulose cell wall
Chloroplasts
Large permanent vacuole (with tonoplast)
Plasmodesmata
Which structures do typical animal cells have that typical plant cells lack?
Centrioles.
Animal cells also have no cell wall, giving them an irregular shape, whereas plant cells have a fixed, regular shape.
Name structures found in both plant and animal cells.
Cell surface membrane
Nucleus
Cytoplasm
Mitochondria
Ribosomes
Rough and smooth ER
Golgi body
How can you identify a plant cell in an electron micrograph?
Look for a cellulose cell wall, chloroplasts and a large central vacuole — these are absent in animal cells.
How can you identify a typical animal cell in an electron micrograph?
It has no cell wall, no chloroplasts and no large vacuole, giving it a rounded, irregular shape.
Centrioles may be visible.
In a micrograph, the presence of a cellulose cell wall and chloroplasts identifies the cell as a cell.
In a micrograph, the presence of a cellulose cell wall and chloroplasts identifies the cell as a plant cell.
True or False?
Both plant and animal cells contain mitochondria.
True.
Mitochondria are found in both, as both carry out aerobic respiration.
What does ATP stand for?
Adenosine triphosphate.
How do cells produce ATP?
Cells produce ATP during respiration, which mainly takes place in the mitochondria.
What is the role of ATP in cells?
ATP is the energy currency of the cell.
It supplies energy for energy-requiring processes in the cell.
Give three examples of energy-requiring processes that use ATP.
Active transport
Muscle contraction
Synthesis of large molecules (e.g. proteins)
Cells use from respiration as the energy source for energy-requiring processes.
Cells use ATP from respiration as the energy source for energy-requiring processes.
What is a prokaryotic cell?
A cell with no nucleus and no membrane-bound organelles, e.g. a bacterium.
Outline the key structural features of a typical prokaryotic (bacterial) cell.
Unicellular
Generally 1-5 µm in diameter
Peptidoglycan cell wall
Circular DNA (not in a nucleus)
70S ribosomes
No organelles surrounded by double membranes
What is the cell wall of a bacterium made of?
Peptidoglycan.
State three differences between a prokaryotic and a eukaryotic cell.
Prokaryotic cells have no nucleus (DNA is free in the cytoplasm); eukaryotic cells have a nucleus.
Prokaryotic cells have no membrane-bound organelles; eukaryotic cells do.
Prokaryotic cells have 70S ribosomes; eukaryotic cells have 80S ribosomes in the cytoplasm.
What features do prokaryotic and eukaryotic cells have in common?
Cell surface membrane
Cytoplasm
Ribosomes
DNA as genetic material
The ribosomes found in prokaryotic cells are of the type.
The ribosomes found in prokaryotic cells are of the 70S type.
True or False?
Prokaryotic cells contain mitochondria.
False.
Prokaryotic cells have no membrane-bound organelles, so they have no mitochondria.
Why are viruses described as non-cellular?
Viruses are not made of cells — they have no cytoplasm, no organelles and no cell surface membrane of their own.
Describe the basic structure of a virus.
A nucleic acid core — either DNA or RNA
A protein coat called a capsid
Some viruses also have an outer envelope made of phospholipids
What is a capsid?
The protein coat that surrounds and protects the nucleic acid core of a virus.
What is the outer envelope of some viruses made of?
Phospholipids.
The genetic material in the core of a virus is either DNA or .
The genetic material in the core of a virus is either DNA or RNA.
True or False?
All viruses have an outer phospholipid envelope.
False.
Only some viruses have a phospholipid envelope; all viruses have a nucleic acid core and a protein capsid.
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